Impact of a long-term crop-livestock system on the physical and hydraulic properties of an Oxisol

Abstract

Intensive cattle grazing and machine traffic may negatively affect soil structure, hydrologic processes and plant development in integrated crop-livestock systems. The pasture management is the critical factor controlling the efficiency of crop-livestock systems, because soil compaction by animal trampling can reduce the soil quality and system productivity. We aimed to study the effects of pasture management and animal trampling on soil physical attributes and water infiltration in a long-term no-tillage and integrated crop-livestock system in Subtropical Brazil. The long-term experiment of an integrated soybean-beef cattle grazing system was conducted in southern Brazil in a randomized block design with five treatment and three blocks. Pasture (Italian ryegrass and black oat) was grazed in the autumn/winter, with sward heights of 10, 20, 30, 40 cm and an ungrazed treatment, while soybean was grown in the spring/summer season. Soil physical attributes (bulk density, soil porosity and water retention curve) and water infiltration were evaluated after 14 years of started the integrated system. The soil physical properties at 0–5 cm depth were strongly affected by cattle grazing, especially in the pastures with sward heights of 10 cm and 20 cm. Consequently, there was a reduction in the water infiltration rate of 81% after grazing, and 47% after soybean harvest, and in pasture with a sward height of 10 cm, when compared with the ungrazed area. Pasture at 10 and 20 cm sward height decreased the water content at matric potentials between −1 and −10 kPa and increased water content between -10 and -1500 kPa, decreasing soil aeration and water availability. Higher soil available water content was found at the moderate grazing intensities of 30 cm and 40 cm pasture sward height. For the sustainability of the integrated soybean-cattle system the results suggest that well-managed grazing systems (30 cm of pasture sward height) should have beneficial soil physical conditions and water infiltration to promote sustainability and limit soil degradation.